“That’s cool, I didn’t know he was playing it,” she said of the scene, remembering it in the script but unaware that Peter had been cast in the role. “That’s one of the great things about ‘Eclipse,’ is that Stephenie [Meyer] goes into some of the backstories of ‘How did the wolves come to be?’ and ‘How did Rosalie come to be?’ and ‘How did Jasper come to be?’”

“I got to actually write those scenes, and have them come alive and explore some backstories,” she explained of her script for the third “Twilight” movie, due in theaters next summer. “[Those flashback scenes] are always, for me, very compelling.”

As Billy explained, Peter was cast as “an old Spanish, sort of unrelated vampire, in a flashback sequence” involving Billy Black (Gil Birmingham) telling the origins of the Quileuete wolves.

“[Peter] is involved in telling the story of how the wolves came to be,” Melissa revealed. “He is one of the provocateurs of the wolves way back when — he sort of starts the whole thing rolling.”

As fans know, much of the tension in the “Twilight Saga” revolves around a careful balance that has kept the vampires and werewolves of Forks living in relative peace for decades — until Bella Swan comes along, that is. Peter’s flashback will detail the evolution of the wolves, and shed further details on how the Quileute and Cullens forged their pact.

“Eclipse” hits theaters everywhere June 30, 2010.

Hey Twilighters: Which ‘Eclipse’ flashback are you most eager to see seven months from now?